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ISLAND LIFE. 
[part II. 
species; and we may be sure that at the time when such 
animals as apes and buffaloes existed, the Asiatic continent 
swarmed with varied forms of mammals to quite as great an 
extent as Borneo does now. If the portion of separated land 
had been anything like as large as Celebes now is, it would 
certainly have preserved a far more abundant and varied fauna. 
To explain the facts we have the choice of two theories ; — 
either that the original island has since its separation been 
greatly reduced by submersion, so as to lead to the extinction 
of most of the higher land animals ; or, that it originally formed 
part of an independent land stretching eastward, and was only 
united with the Asiatic continent for a short period, or perhaps 
even never united at . all, but so connected by intervening 
islands separated by narrow straits that a few mammals might 
find their way across. The latter supposition appears best to 
explain the facts. The three animals in question are such as 
might readily pass over narrow straits from island to island; 
and we are thus better enabled to understand the complete 
absence of the arboreal monkeys, of the Insectivora, and of the 
very numerous and varied Carnivora and Kodents of Borneo, 
all of which are entirely unrepresented in Celebes by any 
peculiar and ancient forms except the squirrels. 
The question at issue can only be finally determined by 
geological investigations. If Celebes has once formed part of 
Asia, and participated in its rich mammalian fauna which has 
been since destroyed by submergence, then some remains of 
this fauna must certainly be preserved in caves or late Tertiary 
deposits, and proofs of the submergence itself will be found 
when sought for. If, on the other hand, the existing animals 
fairly represent those which have ever reached the island, then 
no such remains will be discovered, and there need be no 
evidence of any great and extensive subsidence in late Tertiary 
times. 
Birds of Celebes . — Having thus clearly placed before us the 
problem presented by the mammalian fauna of Celebes, we 
may proceed to see what additional evidence is afforded by 
the birds, and any other groups of which we have sufficient 
information. About 164 species of true land-birds are now 
